The present invention relates to a method of creating multiple fractures in an earth formation surrounding a wellbore formed in the earth formation. It is general practice to create such fractures to stimulate hydrocarbon fluid production from the earth formation, or to provide a flow path for injection fluid. In many instances the formation is to be fractured at different depth levels along the wellbore, for example in case hydrocarbon fluid is to be produced from earth layers at different along hole distances. A normal procedure for creating fractures is to perforate the wellbore casing at the required depth and to pump fracturing fluid into the formation via the casing perforations. Thereafter the fractures are subjected to treatment process, for example by pumping an acid into the fractures, or pumping propant material into the fractures in order to prevent closure of the fractures. A problem arises in case after treatment of the fractures created at a first location, fracturing fluid is pumped into the wellbore in order to create fractures at a second location since any penetration of fracturing fluid into the fractures at the first location will negatively affect the treatment results of such fractures.
Accordingly it is an object of the invention to provide a method of creating multiple fractures in an earth formation surrounding a wellbore, whereby earlier created fractures are not negatively affected by the creation of later fractures.
In accordance with the invention there is provided a method of creating multiple fractures in an earth formation surrounding a wellbore formed in the earth formation, the method comprising
sealing a first section of the wellbore from the remainder of the wellbore by arranging a primary seal assembly in the wellbore, the first section containing a first body of fluid and being located between the primary seal assembly and the wellbore bottom;
pressurising the first body of fluid so as to fracture the earth formation surrounding the first section;
sealing a second section of the wellbore from the remainder of the wellbore by arranging a secondary seal assembly in the wellbore uphole the primary seal assembly, the second section containing a second body of fluid and being located between the secondary seal assembly and the primary seal assembly;
supporting the primary seal assembly by a first support member extending between the primary seal assembly and the wellbore bottom; and
pressurising the second body of fluid so as to fracture the earth formation surrounding the second wellbore section.
By supporting the primary seal assembly relative to the wellbore bottom it is achieved that the second wellbore section is adequately sealed from the fractures created around the first wellbore section.